1. Field of Use
This invention relates to filament wound pressure vessels having threaded openings and to closure thereof. This invention, more particularly, relates to reinforcing the threads in these openings against significant axial forces generated from within the pressure vessels. This invention, still more particularly, relates to increasing the resistance of these threaded openings to such internal forces through the filamentary reinforcement pattern wound into the threads and to accomplishing such reinforcement pattern in an industrially expedient fashion.
2. Prior Art
U.S. Pat. No. 3,124,001 discloses pressure vessels said to resist external pressure by means of internal, filament wound ribs. The pressure vessels in U.S. Pat. No. 3,124,001 have threaded polar openings. The threads are formed using saturated glass fiber fabric pulled down into a thread former with a tow of glass fiber. Such a thread design is unsuited to provide threaded openings whose closure resists significant internal pressures.
UK Pat. No. 1,453,680 discloses threaded polar openings in a rocket motor case wherein the threads are formed by causing continuous filament to track the inwardly extending contours of a thread former. Threads made in this manner will not resist the significant axial forces witnessed in the closure of large diameter openings of tactical rocket motors.
Certain other rocket motor cases have been proposed or made to include a single layer of continuous, uniaxial filament cut and pulled down into the thread former. However, the axial reinforcement of the threaded openings in these pressure vessels is included above the threads; such higher level axial reinforcement is insufficient to resist the magnitude of internal pressures witnessed by larger diameter polar openings of tactical rocket motor cases.